Bone Anchor Assembly, Bone Plate System, And Method

ABSTRACT

In one aspect, a bone anchor assembly is provided having a bone anchor with a head, a resilient locking cap extending about a portion of the bone anchor head, and a cap drive member having a depending annular wall. The annular wall and locking cap have engagement surfaces configured to engage and expand the locking cap as the cap drive member is shifted from an unlocked to a locked position. In another form, a bone plate system is provided including a bone plate having an elongated throughbore and a resilient support member received therein. The support member has an opening sized to receive a bone anchor head and an actuator device carried thereon. The bone plate and support member have interfering portions configured to be shifted to a locked orientation to lock the support member and the bone anchor head at an axial position in the throughbore.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/580,055, filed Dec. 23, 2011, which is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to bone plate systems and, more particularly, tobone plate systems for stabilizing one or more bones.

BACKGROUND OF THE INVENTION

There are presently many different types of bone plate systems forsecuring bones so that the secured bones may fuse or heal. As usedherein, the term bone may refer to a bone, a bone fragment, or a portionof a bone. Bone plate systems often utilize a bone plate havingthroughbores and bone screw assemblies that are driven through thethroughbores and into the underlying bone for securing the bone plate toone or more bones. In some applications, the bone screw assembliesinclude a bone screw that is driven into bone and a device associatedwith the bone screw for restricting back-out of the bone screw once thebone anchor assembly has been seated in the throughbore of the boneplate. The device may include a resilient head of the bone screw forbeing seated within one of the throughbores and a set screw that isthreaded into the resilient head to expand the head against walls of thethroughbore and restrict back-out of the bone screw. However, theresilient head is weaker than the remainder of the bone screw in orderto permit expansion of the head as the set screw is threaded into thehead. Further, the set screw is relatively small and may be difficult tothread into the bone screw head during surgery.

Another type of bone plate system utilizes bone screws having heads withresilient c-rings carried thereon and locking members disposed withinthe bone screws for restricting back-out of the bone screws fromthroughbores of the bone plate. Once the heads of the bone screws havebeen seated within the throughbores, the locking members arelongitudinally shifted within the bone screw to radially expand thec-ring into engagement with walls of the throughbore. The c-ring has anouter annular portion for engaging the throughbore walls and inner,radially extending portions configured to contact the locking member andshift the outer annular portion radially outward with longitudinalshifting of the locking member. However, the radially extending portionsare thin and may deflect when loads are applied to bone screw, such aspost-operation movement of the patient. Deflection of the radiallyextending portions may, over time, reduce the strength of radiallyextending portions and the overall stability of the bone plate system.

In some instances, a predetermined amount of pivoting between a bonescrew and a bone plate of a bone plate system is desired to accommodatesettling of the bones. The pivoting is preferably controlled movement,rather than free movement between the bone screw and bone plate whichmay interfere with fusion of the bones. Although bone screws havingc-ring back-out prevention devices may be used in these applications,the c-rings themselves have an outer surface for engaging the bone platethroughbore walls that is relatively thin compared to the bone screwhead, e.g., less than a quarter of the height of the bone screw head.The short vertical extent of the c-ring outer surface along thethroughbore wall limits the contact area and frictional engagementbetween the c-ring outer surface and the throughbore wall. This isundesirable in some instances because the limited frictional engagementprovided by the c-ring limits the ability of the expanded c-ring tocontrol pivoting of the bone screw relative to the bone plate.

Another shortcoming of prior bone plate systems is the ability to use asingle bone plate system for a variety of patient anatomies. Forexample, to stabilize a pair of vertebrae, an intervertebral implant isinserted between the vertebrae and a bone plate system is connected tothe vertebrae to secure the vertebrae and the intervertebral implanttogether. The intervertebral implant may be selected from a number ofdifferent shapes and sizes to conform to the patient's anatomy. Due tothe possible variation in the intervertebral implant selected for aparticular patient, the bone plate system subsequently used to securethe bones should accommodate the range of shapes and sizes of theintervertebral implant that may be used. One prior approach to providingsuch a bone plate system utilized a bone plate having elongatedthroughbores. The bone plate is first positioned on a pair of vertebraestabilized by an intervertebral implant, and then bone screws are driveninto the elongated throughbores at locations along the throughbores thatpermit the bone screws to engage the underlying vertebrae. Although theelongated throughbores provide flexibility in installation, the bonescrews can slide along the elongated throughbore as the vertebraesettle. In some instances, this post-operative sliding of the bonescrews is undesirable due to the corresponding changes in position ofthe vertebrae.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a bone anchor assemblyis provided that can be driven into bone and securely fixed to a boneplate to secure the bone plate to the bone. The bone anchor assemblyincludes a bone anchor having a head, a resilient locking cap extendingabout a portion of the bone anchor head, and a cap drive member with adepending annular wall for fitting about the bone anchor head portion.The depending annular wall is disposed radially between the bone anchorhead portion and the locking cap. The depending annular wall can therebydirectly transfer loading between and bone anchor head portion and thelocking cap with substantially no deflection or other flexing of thelocking cap, which strengthens the connection between the bone anchorassembly and the bone plate.

To radially expand the locking cap, the cap drive member is shiftableaxially along an outer periphery of the bone anchor portion. The capdrive member and the locking cap have engagement surfaces configured toengage and radially expand the locking cap as the cap drive membershifts axially from an unlocked to a locked configuration. Theengagement surfaces of the cap drive member and locking cap are engagedabout and radially adjacent to the bone anchor head portion. In oneform, the bone anchor head has drive structure disposed radially inwardfrom the bone anchor head portion, the drive structure being configuredto receive a driving tool for driving the bone anchor into bone. Becausethe engagement surfaces of the cap drive member and the locking cap areengaged about the bone anchor head portion and radially outward from thedrive structure, the drive structure of the bone screw is unobstructedby the engagement surfaces of the cap drive member and the locking capwhich permits a wide variety of different types of drive structures tobe used, such as Torx, hex, and Phillips-type, without being limited bythe engagement surfaces of the cap drive member and the locking cap.Further, the bone anchor head is preferably rigid and positioning theengagement surfaces about and radially adjacent to the bone anchor headportion permits the cap drive member to expand the locking cap andsecure the bone anchor assembly to a bone plate without the use of aweakened, resilient bone screw head as in some prior approaches.

A bone plate system is also provided that may be manipulated to adjustthe location of a bone anchor within the bone plate system and allow thebone plate system to conform to the anatomy of a patient and thesurgical procedure being performed. The bone plate system has a boneplate, a plurality of bone anchors for inserting into throughbores ofthe bone plate, and a resilient support member received in an elongatedthroughbore of the bone plate. One of the bone anchors has a head and anactuator device carried thereon, and the resilient support member has anopening sized to receive the bone anchor head and the actuator device.The bone plate and support member are configured to permit movement ofthe support member toward either end of the elongated throughbore beforethe bone anchor is driven into the support member opening, which permitsthe support member to be positioned at a desired location along theelongated throughbore. The location of the resilient support memberalong the throughbore is preferably chosen such that the support memberopening is disposed adjacent an underlying bone to permit the boneanchor to be driven through the support member opening and into thebone. By allowing the resilient support member to be moved along theelongated throughbore to a desired location, the bone plate system canaccommodate a wider range of possible installation configurations thanif the all locations for bone anchors on the plate were static.

For example, if the bone plate system is being used to stabilize a pairof vertebrae on either side of an interverterbral implant, the resilientsupport member can be moved toward one end of the elongated throughboreif the interverterbral implant selected is relatively large, or towardthe opposite end of the elongated throughbore if the interverterbralimplant is relatively small, before driving the bone anchor into theopening of the support member. The resilient support member may also bemoved along the elongated throughbore to permit placement of theassociated bone anchor into a region of a bone that avoids previouslyimplanted hardware in the bone. For example, if a pedicle screw ispresent in a vertebra, the bone plate may be placed against the vertebraand the resilient support member moved to a position along thethroughbore that allows the associated bone anchor to be driven into thevertebral body away from the pedicle screw. This is particularlyadvantageous when the bone plate system is installed using a lateralapproach because the bone anchor can be secured to the vertebral bodywithout having to remove the pedicle screw, which may require aposterior incision and corresponding operation.

The bone plate system also permits the resilient support member and boneanchor received therein to be locked at a selected location along theelongated throughbore. More specifically, the actuator device of thebone anchor may be driven between unlocked and locked positions once thebone anchor head has been received within the support member opening.The resilient support member is expandable and is configured to expandwith driving of the actuator device between the unlocked and lockedpositions. To lock the position of the support member along theelongated throughbore, the resilient support member and bone plate haveinterfering portions that are configured to be in a fixed or lockedorientation relative to each other when the bone anchor actuator devicehas been driven to the locked position. This keeps the support member,and the bone anchor head received therein, at a selected position alongthe elongated throughbore against movement toward either end thereof.The bone anchor head may thereby be seated in the support memberopening, the actuator device driven to the locked position, and the boneanchor and resilient support member locked at the selected axialposition along the throughbore. Thus, the bone plate system providessignificant installation flexibility without post-operative translationof the bone anchor along the elongated throughbore.

In another aspect, a method of securing a bone plate to a bone isprovided that permits the bone plate to be adjusted to conform to thesurgical site before installing the bone plate. The method includesmoving a resilient support member disposed within an elongatedthroughbore of the bone plate along a longitudinal axis of thethroughbore to a selected axial position along the throughbore. Theaxial position of the resilient support member is chosen to orient athrough opening of the resilient support member adjacent a bone so thata shank of a bone anchor may be driven through the support memberthrough opening and into the bone. The method further includes seating ahead of the bone anchor and an actuator device carried thereon in thesupport member through opening, driving the actuator device from anunlocked to a locked position, and expanding the support member towardwalls of the elongated throughbore as the actuator device is driven tothe locked position. The support member and the bone anchor are therebylocked at the selected axial position along the throughbore to resistmovement of the bone anchor along the elongated throughbore and theassociated translational movement of the bone relative to the boneplate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a bone plate system in accordance withthe present invention showing a bone plate and a pair of bone anchorassemblies connected thereto;

FIG. 2 is a perspective view of one of the bone anchor assemblies ofFIG. 1 showing a bone screw, cap drive member, and a resilient lockingcap of the bone anchor assembly;

FIG. 3 is an elevational view of one of the bone anchor assemblies ofFIG. 1 showing the cap drive member of the bone anchor assembly in anunlocked position;

FIG. 4 is an elevational view similar to FIG. 3 showing the cap drivemember shifted to a locked position which radially expands the resilientlocking cap of the bone anchor assembly;

FIG. 5 is a top plan view of the bone plate system of FIG. 1 showing oneof the bone anchor assemblies received in a resilient support member inan elongated throughbore of the bone plate and the other bone anchorassembly received in a non-elongated throughbore of the bone plate;

FIG. 6 is a cross-sectional view taken across line 6-6 in FIG. 5 showinga head portion of the bone anchor assembly received in the resilientsupport member with the cap drive member of the bone anchor assembly inthe unlocked position;

FIG. 7 is a cross-sectional view similar to FIG. 6 showing the cap drivemember shifted to the locked position which expands the locking cap andthe resilient support member of the bone plate;

FIG. 8 is a partial, enlarged view of the area shown in the dashedcircle of FIG. 5 showing projections of the resilient support memberspaced from teeth of the bone plate before the cap drive member has beendriven to the locked position;

FIG. 9 is a partial, enlarged view similar to FIG. 8 showing theprojections of the support member engaged with the teeth of the boneplate after the cap drive member of the bone anchor assembly has beendriven to the locked position;

FIG. 10 is a cross-sectional view taken across line 10-10 in FIG. 5showing generally spherical head portions of the bone anchor assembliesreceived in partially spherical pockets of the resilient support memberand the non-elongated throughbore;

FIG. 11 is a top plan view of the bone plate system of FIG. 1 with thebone anchor assemblies removed to show an opening of the resilientsupport member in which one of the bone anchor assemblies is received;

FIG. 12 is a bottom plan view of the bone plate of FIG. 1 showing agenerally rectangular lower opening of the elongated throughbore and agenerally rectangular lower portion of the support member fit within thelower opening of the elongated throughbore;

FIG. 13 is a perspective view of the resilient support member of thebone plate system of FIG. 1 showing a split-ring configuration of thesupport member;

FIG. 14 is a top plan view of the support member of FIG. 13 showing theprojections of the support member extending radially outward forengaging the teeth of the bone plate;

FIG. 15 is a bottom plan view of the support member of FIG. 13 showingthe flange of the support member extending radially beyond the generallyrectangular lower portion of the support member;

FIG. 16 is an exploded elevational view of one of the bone anchorassemblies of FIG. 1;

FIG. 17 is an elevational view of the bone screw of the bone anchorassembly of FIG. 16 showing the head of the bone screw having a roundedlower surface;

FIG. 18 is a top plan view of the bone screw of FIG. 17 showing a recessfor receiving a driving tool;

FIG. 19 is a perspective view of the bone screw of FIG. 17 showing aradially extending bearing surface of the bone screw configured tosupport the resilient locking cap and a threaded wall upstanding fromthe bearing surface;

FIG. 20 is a cross-sectional view taken across line 20-20 in FIG. 18showing a central axial bore for receiving a screw retention portion ofthe driving tool;

FIG. 21 is an elevational view of the resilient locking cap of the boneanchor assembly of FIG. 16 showing a rounded outer surface of theresilient locking cap;

FIG. 22 is a top plan view of the locking cap of FIG. 21 showing anouter annular wall and radially extending portions of the locking cap;

FIG. 23 is a perspective view of the locking cap of FIG. 1 showing a gapspacing between ends of the locking cap;

FIG. 24 is a cross-sectional view taken across line 24-24 in FIG. 22showing radially inner inclined surfaces against which the cap drivemember cams;

FIG. 25 is an elevational view of the cap drive member of the bone screwof FIG. 16 showing a radially outer, inclined surface of the cap drivemember configured to engage the radially inner inclined surfaces of thelocking cap;

FIG. 26 is a top plan view of the cap drive member of FIG. 17 showing acentral opening of the cap drive member;

FIG. 27 is a perspective view of the cap drive member of FIG. 17 showingstructures of the cap drive member disposed about the central openingconfigured to engage a locking tool;

FIG. 28 is a cross-sectional view taken along line 28-28 in FIG. 26showing an outer profile of the cap drive member;

FIG. 29 is an elevational view of an inserter tool configured to be usedto insert the bone plate of FIG. 1 during surgery;

FIG. 29A is a top plan view of the inserter tool of FIG. 29 showing thebone plate in a generally parallel orientation relative to a shaft ofthe inserter tool;

FIG. 30 is an enlarged partial view of a distal end of the inserter toolof FIG. 29 showing the distal end connected to the bone plate;

FIG. 31 is an enlarged elevational view of the distal end of theinserter tool of FIG. 29 showing a linkage between the shaft and a pivotbody of the inserter tool which is connected to the bone plate;

FIG. 32 is an elevational view similar to FIG. 29 showing a lever of thetool moved toward a handle of the tool which causes the inserter tool topivot the bone plate;

FIG. 32A is a top plan view of the inserter tool of FIG. 32 showing thebone plate pivoted to a generally perpendicular orientation relative tothe inserter tool shaft;

FIG. 33 is an enlarged partial view of the distal end of the insertertool of FIG. 32 showing the distal end connected to the bone plate;

FIG. 34 is an exploded schematic view of the inserter tool of FIG. 29showing a body shaft, a pivot shaft, and a grip control shaft of theinserter tool;

FIG. 35A is a cross-sectional view of the inserter tool taken acrossline 35A-35A in FIG. 29A showing the lever in the open position and apivot shaft of the inserter tool shifted distally;

FIG. 35B is a cross-sectional view of the inserter tool taken acrossline 35B-35B in FIG. 32B showing the lever in the closed position andthe pivot shaft shifted proximally with the bone plate removed forclarity;

FIG. 36 is an elevational view of the distal end of the inserter tool ofFIG. 29 with the bone plate removed therefrom showing a gripping portionof the inserter tool and arms of the gripping portion in a releaseconfiguration;

FIG. 37 is an elevational view similar to FIG. 36 showing the grippingportion arms in an engagement configuration;

FIGS. 38 and 39 are enlarged cross-sectional views generally takenacross line 35B-35B in FIG. 32A showing the gripping portion arms in therelease and engagement configurations;

FIGS. 40 and 41 are bottom plan views of the bone plate connected to thedistal end of the inserter tool showing the gripping portion arms in therelease and engagement configurations;

FIGS. 42 and 43 are views of the handle of the inserter tool showing anouter profile of the handle;

FIGS. 44-52 illustrate a method of implanting the bone plate system ofFIG. 1;

FIG. 53 is a left side elevational view of another inserter toolconfigured to be used to insert the bone plate of FIG. 1 during surgery;

FIG. 54 is right side perspective view of the inserter tool of FIG. 53showing the inserter tool partially disassembled including a pivotsleeve of the inserter tool disconnected from a lever of the tool andpivoted away from a shaft of the inserter tool;

FIG. 55 is an exploded schematic view of the inserter tool of FIG. 53showing a body shaft, the pivot sleeve, and a pivot control shaft of theinserter tool;

FIG. 56 is an enlarged right side perspective view of the inserter toolof FIG. 53 showing the pivot sleeve connected to the lever;

FIG. 57 is a cross-sectional view of the inserter tool of FIG. 53showing a lever of the inserter tool in an open position;

FIG. 58 is a cross-sectional view similar to FIG. 57 showing the leverin a closed position;

FIGS. 59 and 60 are enlarged, elevational views of different sides ofthe inserter tool of FIG. 53 showing arms of the body shaft whichsupport a pivot body of the distal end of the inserter tool;

FIG. 61 is an enlarged plan view of the distal end of the insertershowing the pivot body pivoted relative to the body shaft;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 11, a bone plate system 10 is providedhaving a bone plate 12 with a bone plate member 14 and a movableresilient support member 16. The support member 16 may be moved along anelongated throughbore 18 of the bone plate member 14 to provideflexibility during installation of the bone plate system 10. Morespecifically, the bone plate system 10 includes a pair of bone anchorassemblies 20, 24 for securing the bone plate 12 to a pair of bones,with the bone anchor assembly 20 being driven into an opening 53 of thesupport member 16 and a bone anchor assembly 24 being driven into anon-elongated throughbore 22 of the bone plate member 14 (see FIG. 11).The bone anchor assemblies 20, 24 are preferably preassembled for easeof handling during surgery and can be readily driven into the supportmember opening 53 and bone plate throughbore 22 to secure the bone plate12 to bones. Before the bone anchor assembly 20 is driven into thesupport member opening 53, the resilient support member 16 may be movedwithin the elongated throughbore 18 to increase or decrease the distancebetween the support member opening 53 and the non-elongated throughbore22, and the resulting positions of the bone anchor assemblies 20, 24, inorder to permit the bone anchor assemblies 20, 24 to be driven intodesired areas of the underlying bones. Once the bone anchor assembly 20has been driven into the support member opening 53 and received therein,the support member 16 and the bone anchor assembly 20 may be secured ata desired location along the throughbore 18 to restrict translationalmovement of the bone anchor assemblies 20, 24 relative to each other, asdiscussed in greater detail below. Thus, the bone plate system 10provides enhanced flexibility during installation by allowing theposition of the support member 16 within the elongated throughbore 18 tobe adjusted in situ to conform to the anatomy of the patient beforesecuring the bone plate 12 to the bones using the bone anchor assemblies20, 24.

With reference to FIG. 2, the bone anchor assemblies 20, 24 are similarand each have a bone anchor, such as a bone screw 26, for engaging abone. The bone screw 26 has a bone screw head 30 and an actuator device32 carried thereon, as shown in FIG. 2. The actuator device 32 isconfigured to be driven to a locked position after the bone screw 26 hasbeen seated within the support member opening 53. Driving the actuatordevice 32 of the bone anchor assembly 20 to the locked position tightlyengages the bone anchor assembly 20 with the support member 16. Drivingthe actuator device 32 of the bone anchor assembly 20 also locks thesupport member 16 to the bone plate member 14 at a selected positionalong the elongated throughbore 18, as discussed in greater detailbelow. Similarly, driving the actuator device 32 of the bone anchorassembly 24 to its locked position tightly engages the bone anchorassembly 24 to the plate member 14 within the non-elongated throughbore22.

In one form, the actuator device 32 includes a cap drive member 34connected to the bone screw head 30 and a resilient locking cap 36disposed on the bone screw head 30, as shown in FIG. 2. The connectionbetween the cap drive member 34 and the bone screw head 30 may be athreaded engagement so that clockwise rotation of the cap drive member34 in direction 40 about a longitudinal axis 42 of the bone anchorassembly 20 advances the cap drive member 34 in direction 46 toward thebone screw head 30, as shown in FIGS. 3 and 4. Movement of the cap drivemember 34 in direction 46 toward the bone screw head 30 causes outwardexpansion of the locking cap 36 in directions 60, 62, which expands thesupport member 16 and secures the support member 16 and bone anchorassembly 20 at a desired position along the elongated throughbore 18.

With reference to FIGS. 6, 7, and 16, the cap drive member 34 has adepending wall 64 extending about a portion of the bone screw head 30,such as screw head upstanding wall 66. The depending wall 64 of the capdrive member 34 is disposed radially between the bone screw wall 66 andthe locking cap 36. The depending wall 64 and the bone screw wall 66each have a generally tubular shape and are concentrically aligned whenthe cap drive member 34 is connected to the bone anchor head 30.Further, the locking cap 36 has a generally annular shape extendingaround the cap drive member 34 when the cap drive member 34 and thelocking cap 36 are connected to the bone screw head 30. The concentricengagement of the bone screw wall 66, cap drive member depending wall64, and locking cap 36 allows the cap drive member depending wall 64 todirectly transfer loading exerted on the locking cap 36, such as loadsfrom post-operative shifting of the vertebra, against the bone screwwall 66 without the use of thin, radially extending members as in someprior bone anchor assemblies. Further, the cap drive member dependingwall 64 can directly transfer loading from the locking cap 36 to thebone screw wall 66 with substantially no deflection or other flexing ofthe cap drive member depending wall 64, which increases the strength ofthe engagement between the bone anchor assemblies 20, 24 and the boneplate 14.

The cap drive member 34 and locking cap 36 have engagement surfaces,such as cam surfaces 50, 52, configured to engage and expand the lockingcap 36 with movement of the cap drive member 34 from an unlocked to alocked position, as shown in FIGS. 6 and 7. The cam surface 50 isdisposed on a radially outer portion 55 (see FIG. 28) of the cap drivemember depending wall 64 and the cam surface 52 is disposed on aradially inner portion 57 (see FIG. 24) of the locking cap 36 so thatthe cam surfaces 50, 52 engage about and radially outward from the bonescrew wall 66. The bone screw head 30 may be substantially rigid, andpositioning the cam surfaces 50, 52 about and radially outward from thebone screw head portion 66 permits the cap drive member 34 to expand thelocking cap 36 without utilizing a weakened screw head as in some priorapproaches.

Another advantage of the cam surfaces 50, 52 of the cap drive member 34and locking cap 36 being disposed about and radially outward from thebone screw wall 66 is that the cam surfaces 50, 52 are positionedoutside of a drive recess 71 of the bone screw head 30, as shown inFIGS. 6 and 7. The drive recess 71 is generally unobstructed by the capdrive member 34 and locking cap 36 so that the size of the drive recess71 can be relatively large without reducing the strength of the capdrive member depending wall 64. Similarly, the bone screw upstandingwall 66 extending about the drive recess 71 can be relatively thick tofurther enhance the strength of the bone screw head 30 withoutcompromising the strength of the locking cap depending wall 64. Thisapproach stands in contrast to some prior bone screw assemblies, whichutilize a c-ring having radially extending portions configured tocontact a locking member. In these prior screw assemblies, increasingthe size of a drive recess of the bone screw assembly required that theradially extending portions be lengthened or that the portions of thebone screw head surrounding the drive recesses be thinned, both of whichreduce the strength of those prior bone screw assemblies.

With reference to FIG. 11, the resilient support member 16 may be movedin directions 48A, 48B along an axis 47 of the elongated throughbore 18before the bone anchor assembly 20 is driven into the opening 53 and thecap drive member 34 shifted to the locked position. This adjustabilityallows a surgeon to position the support member 16 so that the opening53 is adjacent a desired portion of an underlying bone. For example, thebone plate system 10 may be used to stabilize a pair of vertebrae 720,722 with an implant 724 having a width 804 (see FIG. 46). If the implantwidth 804 is relatively large, the support member 16 may be moved indirection 48A in order to increase the distance between the supportmember opening 53 and non-elongated throughbore 22 and the resultingpositioning of the bone anchors 20, 24. The support member 16 can bemoved in direction 48A until the support member opening 53 is locatedadjacent the vertebra 722, for example, so that the bone anchor assembly20 may be driven through the opening 53 and into an end plate of thevertebra. Conversely, if the implant 724 has a smaller width 804, thesupport member 16 may be moved in direction 48B to decrease the distancebetween the support member opening 53 and the non-elongated throughbore22 and the resulting distance between the bone anchor assemblies 20, 24.

With the support member 16 in the desired location along the elongatedthroughbore 18, the bone anchor assembly 20 may be driven into thesupport member opening 53 and the position of the support member 16 andbone anchor assembly 20 may then be locked along the throughbore 18, asshown in FIGS. 5-7. More specifically, the resilient support member 16has a pair of side portions 72, 74 on opposite sides of the opening 53configured to be engaged by the resilient locking cap 36. The platemember 14 and support member 16 also have interfering portions 90, suchas support member projections 92 and plate member teeth 94, configuredto engage and limit movement of the support member 16 relative to thebone plate member 14, as shown in FIGS. 8 and 9. Shifting the cap drivemember 34 of the bone anchor assembly 20 in direction 46 (see FIGS. 3and 4) to the locked position expands the locking cap 36, presses apartially spherical outer surface 100 of the locking cap 36 against apocket surface 103 of the support member 16, and shifts support memberportions 72, 74 apart in directions 76, 78 toward throughbore walls 80,82, as shown in FIGS. 6 and 7.

Expansion of the resilient support member 16 shifts the support memberprojections 92 and plate member teeth 94 from an adjustment orientation,where there is a gap spacing 96 between the projections 92 and teeth 94,into a locked orientation where the projections 92 and teeth 94 areengaged, as shown in FIGS. 8 and 9. The engaged projections 92 and teeth94 restrict translational movement of the support member 16 and boneanchor assembly 20 received therein along the elongated throughbore 18.Thus, the support member projections 92 and bone plate teeth 94 can bequickly shifted from the adjustment orientation to the lockedorientation to lock the position of the support member 16 and boneanchor assembly 20 simply by shifting the cap drive member 34 to thelocked position after the bone screw head 30 has been seated in theopening 53. This easy-to-use location locking mechanism advantageouslyprovides the bone anchor stability of a bone plate having static boneanchor locations as well as the installation flexibility of a bone platehaving elongated throughbores. Further, the engaged projections 92 andteeth 94 may also restrict rotation of the support member 16 about thebone anchor longitudinal axis 46 within the throughbore 18 to increasethe stability of the bone anchor 20 within the elongated throughbore 18.

In one form, the tolerances between the support member projections 92and bone plate teeth 94 produce a slight ratcheting action when theprojections 92 and teeth 94 are in the adjustment orientation and thesupport member 16 is moved along the elongated throughbore 18. Theslight ratcheting action may be desirable in some applications torestrict the support member 16 from moving out of a desired positionalong the throughbore 18 before the bone anchor assembly 20 is driveninto the support member opening 53 (see FIG. 48). In another form, thesupport member projections 92 and the bone plate teeth 94 may be inclearance with one another when they are in the adjustment orientation.The interfering portions of the support member 16 and the bone platemember 14 may have a variety of possible configurations. For example,the interfering portions may include one or more pins located on thesupport member 16 and one or more corresponding recesses on the boneplate member 14. In another approach, the interfering portions mayinclude one or more tabs of the support member 16 and one or morecorresponding slots on the bone plate member 14.

With reference to FIGS. 3 and 4, shifting the cap drive member 34 to thelocked position shifts the partially spherical outer surface 100 of thelocking cap 36 radially outward until the outer surface 100 is generallyflush with a partially spherical lower surface 102 of the screw head 30.With the locking cap 36 in its expanded configuration, the surfaces 100,102 form a larger, partially spherical outer surface 95 of a headportion of the bone anchor assembly 20. Further, the support member 16has the partially spherical pocket surface 103 and the non-elongatedthroughbore 22 has a partially spherical pocket surface 120 each with arespective radius of curvature that is complimentary to the curvaturesof the outer surfaces 100, 102 with the locking caps 36 in theirexpanded configurations, as shown in FIG. 10. The head portions 97 ofthe bone anchor assemblies 20, 24 thereby form a ball-and-socketconnection between the bone anchor assemblies 20, 24 and the bone plate12. The ball-and-socket connections permit a controlled pivoting of thebone anchor assemblies 20, 24 to accommodate post-operative movement ofthe bones.

With reference to FIGS. 6 and 7, driving the bone anchor 26 into thesupport member opening 53 also seats the screw head lower surface 102against a seating portion 105 of the pocket surface 103 which can beused to lag the bone plate member 14 against a bone. Further, theengagement between the bone screw head lower surface 102 and the seatingportion 105 of the pocket surface 103 provides a direction connectionbetween the bone screw 26 and the bone plate 12. This direct connectionincreases the strength of the engagement between the bone screw 26 andthe bone plate 12 and permits the bone screw 26 to directly transferloading to the bone plate 12.

The cap drive member 34 is then shifted to the locked position whichexpands the locking cap 36 and brings the cap outer surface 100 intoengagement with an engagement portion 107 of the pocket surface 103.Driving the cap drive member 34 into the locked position firmly engagesthe partially spherical outer surface 100 of the locking cap 36 with theengagement portion 107 of the pocket surface 103. Thus, with the screwhead 30 seated in the support member opening 53 and the cap drive member34 shifted to the locked position, both the cap outer surface 100 andthe head lower surface 102 are frictionally engaged with the supportmember seating surface 103. This frictional engagement providescontrolled resistance to pivoting movement of the bone anchor assembly20 relative to the support member 16.

With reference to FIGS. 3 and 4, the bone anchor assembly head portion97 has a height 99 along the bone anchor assembly longitudinal axis 42and the locking cap partially spherical outer surface 100 has a height101 that is approximately half the height 99 of the bone anchor assemblyhead portion 97. In some forms, the height 101 could be approximately aquarter of the height 99, approximately three-quarters of the height 99,or another proportion although the locking cap height 101 is preferablygreater than a quarter of the head portion height 99 in order topreserve a sufficiently large partially spherical lower surface 102 ofthe bone screw head 30. The relatively large axial extent or height 101of the locking cap outer surface 100 provides a large amount of surfacearea of the locking cap outer surface 100 which can engage the supportmember pocket surface 103. This increases the frictional engagement ofthe locking cap 36 with the support member 16 and limits pivoting of thebone anchor assembly 20 once the cap drive member 34 has been shifted tothe locked position.

With reference to FIG. 10, the partially spherical seating surfaces 103extends along the locking cap outer surfaces 100 substantially theentire length of the outer surface 100 along the longitudinal axis 42 ofthe bone anchor assembly 20. By extending substantially the entire axialextent of the locking cap outer surface 100, the frictional engagementbetween the locking cap outer surface 100 and the support member seatingsurface 103 can be maximized. For example, when the bone screw 20undergoes pivoting (such as due to post-operative movement of bones) orwhen the bone anchor assembly 20 is driven obliquely into the opening 53of the support member 16, there is still a majority of the locking capouter surface 100 engaged with the support member pocket surface 103despite the transverse orientation of the locking cap 36 relative to thesupport member 16. The partially spherical seating surface 120 of thenon-elongated throughbore 22 is similar to the support member seatingsurface 103 and provides similar advantages in terms of engagement andcontrolled pivoting between the bone anchor assembly 24 and the platemember 14.

The materials of the bone screw 26, locking cap 36, and bone platemember 14 may be selected, in part, to provide a desired amount offrictional engagement between the bone anchor assembly 20 and thesupport member 16 which controls pivoting of the bone anchor 20. Thesurface texture of the surfaces 100, 102, 103, and 120 may also beconfigured to provide a desired amount of frictional engagementtherebetween and resulting resistance to pivoting of the bone anchorassemblies 20, 24 relative to the bone plate 12. For example, theroughness of one or more of the surfaces 100, 102, 103, and 120 can beincreased, such as by blasting, in order to increase the frictionalengagement between the support member 16 and the bone anchor assembly 20and increase resistance to pivoting of the bone anchor assembly 20.

With reference to FIGS. 6, 12, and 15, the support member 16 andthroughbore 18 have cooperating features configured to limit rotation ofthe support member 16 and generally restrict the support member 16 tomovement along the axis 47 of the elongated throughbore 18. In one form,the throughbore 18 has a narrow section 150 near a bottom surface 152 ofthe bone plate member 14. The narrow section 150 includes flat guidesurfaces 154, 156 on opposite sides have the throughbore 18 extendingalong the axis 46 of the throughbore 18. The support member 16 has anarrow lower portion 160 configured to fit within the throughbore narrowsection 150 between the guide surfaces 154, 156. The support memberlower portion 160 has a pair of lower walls 162, 164 configured to abutthe guide surfaces 154, 156, as shown in FIGS. 12 and 15. The platemember lower walls 162, 164 engage the support member guide surfaces154, 156 and resist rotary movement of the support member 16 within thethroughbore 18. This further increases the stability of the construct ofthe bone plate member 14, support member 16, and bone anchor assembly20.

With reference to FIGS. 13-15, the support member 16 has a c-ring shapeincluding a pair of opposed ends 180, 182 separated by a gap 184. Thegap 184 permits the ends 180, 182 to move apart with radial expansion ofthe locking cap 36 due to shifting of the cap drive member 34 to thelocked position (see FIGS. 6 and 7). The gap 184 also permits thesupport member 16 to be compressed, with ends 180, 182 shifting towardeach other, during insertion of the support member 16 through anenlarged upper section 186 of the throughbore 18 adjacent an uppersurface 187 of the plate member 14 (see FIGS. 10 and 11). The compressedsupport member 16 may be advanced into the throughbore 18 until a lowersurface 200 of a flange 202 of the support member 16 contacts a lowersupport surface 204 of a channel 206 of the plate member 14, as shown inFIG. 6. The compressed support member 16 may then be released to permitthe ends 180, 182 to expand apart and the flange 202 to shift outwardinto the channel 206. At this point, the resilient support member 16 isretained in the elongated throughbore 18 and may be shifted therealongas discussed above. The engagement between the support member flange 202and the plate member channel 206 permits the bone anchor 20 to lag thebone plate 12 against a bone by seating the bone anchor 30 within thesupport member opening 53. Further, the engagement between the supportmember flange 202 and the plate member channel 206 transfers axialloading between the bone anchor 20 and bone plate 12 and restrictspull-through of the bone anchor assembly 20 out of the elongatedthroughbore 18.

The channel 206 includes sections 210, 212 on opposite sides of thethroughbore 18 (see FIGS. 6 and 7) sized to receive correspondingportions 214, 216 of the support member flange 202 (see FIG. 14). Thesupport member flange 202 has outer surfaces 224, 226 and the channelsections 210, 212 have guide surfaces 228, 230 which guide the supportmember 16 along the throughbore 18, as shown in FIG. 6. With referenceto FIG. 14, the support member 16 has a body 220 with a width of 222selected to permit the projections 92 a, 92 b to be in the adjustmentorientation relative to the bone plate teeth 94 a, 94 b when the supportmember 16 is in the unexpanded configuration. The width 222 alsoprovides a small amount of clearance between the flange outer surfaces224, 226 and the channel guide surfaces 228, 230 which permits thesupport member 16 to be moved longitudinally within the elongatedthroughbore 18. With reference to FIGS. 12 and 15, the narrow section150 of the support member 16 may have a width 240 between the supportmember lower walls 162, 164 which provides slight gaps 225, 227 betweenthe walls 162, 164 and the plate member guide surfaces 154, 156. Thesegaps limit interference between the walls 162, 164 when the supportmember 16 is in the unexpanded and expanded configurations, although thegaps 162, 164 are smaller when the support member has been expanded.Limiting interference between the support member lower walls 162, 164and the plate member guide surfaces 154, 156 may be desirable to ensurethat the support member projections 92A, 92B fully engage the platemember teeth 94A, 94B despite variation in tolerances of the platemember 14, support member 16, and bone anchor assembly 20 duringmanufacturing.

With reference to FIGS. 16-28, the bone anchor assembly 20 is describedin greater detail. The bone screw head 30 has a partially sphericallower surface 102, a shoulder bearing surface 252 extending inward fromthe lower surface 102, and the wall 66 upstanding from the shoulderbearing surface 252. The upstanding wall 66 has a connection structure,such as threads 264, for connecting to the cap drive member 34. Theupstanding wall 66 also includes the drive structure 71 for receiving adriving tool 2000, as shown in FIG. 48. In one form, the drive structure71 includes a drive recess 280 for receiving a distal end of the drivingtool, such as a socket, a hex socket, or a Phillips recess. For example,the drive recess 280 may be a T20 Torx drive to provide a firmengagement between the driving tool 2000 and the bone screw 26 duringinsertion and driving of the bone anchor assemblies 20, 24. The bonescrew head 30 may also have a retention structure 282 configured toengage a retention portion of the driver tool 2000 and maintain the boneanchor assembly 20 on the driving tool 2000 until the bone anchorassembly 20 has been driven into bone. In one form, the retentionstructure 282 has threads 284 configured to engage threads of aninternal retention shaft 2004 (see FIG. 48) of the driving tool 2000.

With reference to FIGS. 21-24, the locking cap 36 has an outer wall 310with a split-ring configuration and engagement members 312 extendinginwardly from the outer wall 310. The engagement members 312 haveretention tips 314 sized to fit within a groove 270 extending around abase of the annular wall 66 (see FIGS. 17 and 20). The retention tips314 have upper stop surfaces 316 that are positioned below a stopsurface 272 of the bone screw groove 270 when the locking cap 36 hasbeen assembled onto the screw head 30. The surfaces 272, 316 are inaxial overlapping relation such that the surfaces 272, 316 contact andrestrict removal of the locking cap 36 in direction 380 (see FIG. 16)once the locking cap 36 has been assembled onto the bone screw head 30.

The locking cap engagement members 312 are generally wedge shaped andtaper radially inward from an upper portion 313 adjacent the cap drivemember 34 toward a lower portion 315 adjacent the shoulder bearingsurface 252 of the bone screw head 30, as shown in FIG. 24. The lockingcap 36 has cutouts 320 between each of the cam members 312 that definethe general wedge shape of each engagement member 312 and increase theflexibility of the locking cap 36, as shown in FIG. 22.

With reference to FIGS. 23 and 24, the locking cap engagement surface 52includes a cam surface 322 on each of the engagement members 312 thatextends obliquely relative to the bone anchor longitudinal axis 46. Thecam surface 322 may extend a majority of the height of the locking cap36 along the anchor axis 46 and taper from a wider upper portion 324 toa narrow lower portion 326 to produce a relatively large amount of areafor the cam surface 322 of each engagement member 312. This increasesthe overall cam surface area of the locking cap 36 and improves the easewith which the locking cap 32 may expand the locking cap 36. Further,the tapered shape of the cam surface 322 provides a surface forcontacting the cap drive member engagement surface 50 while preservingthe general wedge-shape of the engagement members 312 which improves theflexibility of the locking cap 36. The cam surface 322 also extendsradially inward toward the bone screw upstanding wall 66 which permitsthe cap drive member engagement surface 50 to engage the cam surfaces322 even as the locking cap 36 expands away from the upstanding wall 66as the cap drive member 34 reaches its locked position.

With reference to FIGS. 25-28, the cap drive member 34 has an upperdrive portion 401 with a through opening, such as an upper lockingrecess 400, sized to receive both the driving tool 2000 (see FIG. 49)and a distal end 3000 of a final tightener 3002 (see FIG. 51). However,the cap drive member 34 has a locking structure 402 configured to engagethe final tightener 3002. In one form, the locking structure 402 is aT30 Torx socket, which is larger than a T20 Torx socket of the bonescrew drive structure 71. The cap drive member 34 thereby permits afirst tool to be used to drive the bone anchor assemblies 20, 24 intobones, and a different, second tool to be used to perform final lockingof the bone anchor assemblies 20, 24 to the bone plate 12.

In one form, the cap drive member 34 has a lower end portion 403 and theengagement surface 50 includes a cam surface 404 that extends about thelower end portion 403 inwardly and obliquely relative to the bone anchorlongitudinal axis 46. The lower end portion 403 of the cap drive member34 thereby acts as a wedge to expand the locking cap 36 as the cap drivemember 34 is driven to the locked position. The cam surface 404 isdisposed radially outward on the cap drive member 34 and has a largesurface area due to the diameter of the cap drive member 34. The largesurface areas of the cap drive member cam surface 404 and locking capcam surfaces 322 improve force transfer between the cap drive member 34and the locking cap 36. Further, the large surface areas of the capdrive member cam surface 404 and locking cap cam surfaces 322 increasethe frictional engagement between the cap drive member 34 and lockingcap 36 which restricts movement of the cap drive member 34 away from thelocked position.

In one form, the cam surface 404 is annular and continuous about the capdrive member 34 which permits the cam surface 404 to remain engaged withthe cam surfaces 322 of the locking cap 36 as the drive member 34 isrotatably driven to the locked position.

The cap drive member 34 and locking cap 36 are generally assembled in adirection 250 onto the screw head 30 along the longitudinal axis 42 ofthe bone anchor assembly 20, as shown in FIG. 16. The locking cap 36 ispositioned on the shoulder bearing surface 252 (see FIG. 19) of thescrew head 30. Positioning the locking cap 36 onto the bearing surface252 of the bone screw head 30 may include expanding the locking cap 36by moving ends 300, 302 thereof apart to enlarge a gap spacing 304therebetween (see FIG. 22). The locking cap 36 may then be moved axiallydownwardly onto the bone screw head 30 with the upstanding wall 66passing into a lower opening 306 of the locking cap 36 (see FIG. 24).

Next, the lower end portion 403 of the cap drive member 34 is advancedinto a central opening 354 (see FIG. 23) of the locking cap 36. Thelocking cap 36 has retention ribs 372 disposed above the engagementmembers 312 with guide surfaces 356 thereon. Advancing the cap drivemember lower portion 403 into the locking cap central opening 354 bringsthe cap drive member cam surface 404 into contact with tapered guidesurfaces 356 of the locking cap retention ribs 372. Continued axialmovement of the cap drive member 34 toward the bone screw head 30 causesthe cap drive member cam surface 404 to bear against the locking capguide surfaces 356. This partially expands the locking cap 36 andpermits a shoulder 470 of the cap drive member 34 (see FIG. 28) totravel axially beyond the retention ribs 372 of the locking cap 36.

Once the cap drive member shoulder 470 has passed beyond the locking capretention ribs 372, the shoulder 470 has a flat annular stop surface 472that is positioned below stop surfaces 376 on the undersides of theretention ribs 372 of the locking cap 36, as shown in FIGS. 24 and 28.At this point, the stop surfaces 376, 472 are in an axially overlappingand confronting orientation which restricts removal of the cap drivemember 34 from within the locking cap 36 in direction 380 (see FIG. 6).Thus, the stop surfaces 272, 316 and 376, 472 of the bone anchor 26, capdrive member 34, and locking cap 36 maintain the cap drive member 34 andlocking cap 36 on the bone screw head 30 and keep the bone anchors 20,24 in the preassembled configuration.

The components of the bone plate system 10 may be made of biocompatiblematerials, such as stainless steels, titanium or titanium alloys, orother metals or alloys. The components of the bone plate 10 may also bemade of one or more polymers, such as polyether ether ketone (PEEK).

With reference to FIGS. 29-43, an inserter tool 500 is provided forinserting the bone plate 12 into a confined surgical environment andpositioning the bone plate 12 near one or more bones. The inserter tool500 has a distal end portion 502 configured to releasably connect to thebone plate 12 and a proximal end portion 504 with a grippable handle506. The inserter tool 500 has a pivot mechanism 507 configured toselectively pivot the bone plate 12, the pivot mechanism 507 having aninsertion configuration where a longitudinal axis 530 the bone plate 12is oriented generally parallel to a longitudinal axis 532 of a shaft 509of the inserter tool 500 (see FIGS. 29 and 29A) and a positioningconfiguration where the axis 530 of the bone plate 12 is generallyperpendicular to the shaft axis 532 (see FIGS. 32 and 32A). With thepivot mechanism 507 in the insertion configuration, the inserter tooldistal end portion 502 and the plate member 12 connected thereto arerelatively compact, particularly in a lateral direction transverse tothe shaft axis 532, and can be advanced through a surgical channelhaving a smaller cross-section than if the bone plate 12 was extendingperpendicular to the shaft axis 532. The relatively compactconfiguration of the tool distal end portion 502 and plate member 12 canbe seen, for example, by comparing a leading end width 531 of the distalend portion 502 and plate member 12 when the pivot mechanism 507 is inthe insertion configuration (see FIG. 29A) to a leading end width 533when the pivot mechanism 507 is in the positioning configuration (seeFIG. 32A). Because the leading end width 531 is smaller than the width533, the inserter tool distal end portion 502 and plate member 12 may beadvanced through a smaller working channel when the pivot mechanism 507is in the insertion configuration than if the pivot mechanism 507 werein the placement configuration. Thus, the pivot mechanism 507 enablesthe inserter tool 500 to be used in more tightly confined environmentsand provides a significant improvement over inserter tools that cangrasp an implant in only a perpendicular orientation.

Once the inserter tool distal end portion 502 and bone plate 12 reachthe surgical site, the pivot mechanism 507 can be shifted andreconfigured to the positioning configuration where the bone plate 12 isgenerally perpendicular to the shaft 509, as shown in FIGS. 32 and 32A.With the bone plate 12 generally perpendicular to the shaft 509, thehandle 506 can be manipulated to move the bone plate 12 within thesurgical site and position the bone plate 12 at a desired location onone or more bones (see FIGS. 45 and 46). In this manner, the insertertool 500 provides improved ability to advance elongate implants, such asthe bone plate 12, through a small working channel and then pivot theimplant relative to the inserter tool 500 and permit placement of theimplant on one or more bones.

With reference to FIGS. 29 and 34, the inserter tool shaft 509 includesan outer body shaft 522, an intermediate pivot sleeve 520, and an innergrip control shaft 574. The pivot mechanism 507 includes the handle 508,the pivot sleeve 520, and a pivot body 524 connected to a distal end ofthe body shaft 522. Moving or compressing the lever 508 toward thehandle to a closed position causes the pivot sleeve 520 to slideproximally within the body shaft 522 and pivot the pivot body 524approximately 90 degrees about a pivot axis 526, as shown in FIGS. 29,32, 35A, and 35B. The bone plate 12 is connected to the pivot body 524,such that pivoting of the pivot body 524 due to compressing the lever508 causes the bone plate 12 to pivot relative to the inserter toolshaft 509. More specifically, compressing the lever 508 causes the boneplate 12 to move from an insertion orientation where a longitudinal axis530 of the bone plate 12 is generally parallel with a longitudinal axis532 of the shaft 509 to a positioning orientation where the bone platelongitudinal axis 530 is generally perpendicular to the shaft axis 532.The inserter tool 500 has a latch 534 with a hook 536 which may bepivoted to an engaged position where the hook 536 engages a tooth 538 ofthe handle 506. This allows the surgeon to easily maintain the boneplate 12 in the positioning orientation while performing other steps ofthe surgery, as will be discussed in greater detail below. Further, thelatch 534 may be biased to the engagement position by a spring torestrict the latch 534 from being inadvertently disengaged.

With reference to FIGS. 34, 35A, and 35B, the inserter tool 500 includesa spring 540 arranged to bias the pivot sleeve 520 toward the distal endportion 502 of the inserter tool 500. Moving the lever 508 toward thehandle 506 overcomes the bias force from the spring 540 and shifts thesleeve 520 back toward the proximal end portion 504. The outer body 522includes a pair of pins 542 inserted in holes 544 of the body 522 (seeFIG. 34) to support a spring support 546 within the body 522 and preventthe support 544 from traveling in direction 548. Opposite the springsupport 546, there is a second spring support 550 fixed to the pivotsleeve 520 and housed within the body shaft 522 when the inserter tool500 is assembled. Compressing the handle 508 causes the pivot sleeve 520to move in direction 548 toward the proximal end portion 504, whichmoves the spring support 550 mounted on the pivot sleeve 520 indirection 548 and compresses the spring 540 between the supports 546,550. Releasing the handle 508 permits the spring 540 to expand and shiftthe pivot sleeve 520 in direction 556 back toward the distal end portion502.

With reference to FIGS. 35A, 36, and 37, The inserter tool 500 has agripping device 570 that allows the inserter tool 500 to releasinglyengage the bone plate 12. The gripping device 570 includes a gripcontrol member, such as knob 572, and a gripping portion 580 that isconfigured to engage the bone plate 12. In one form, the gripping device570 includes the grip control shaft 574 disposed within the pivot sleeve520 and the knob 572 is threadingly engaged with the grip control shaft574. Rotation of the knob 572 produces longitudinal movement of the gripcontrol shaft 574 within the pivot shaft 520 and manipulates theconfiguration of the gripping portion 580.

For example, the gripping portion 580 may have a plate engagement arm582 and a fixed arm 584 sized to fit into a slot 586 of the plate member14 (see FIGS. 11, 40, and 41). The arm 582 is operably coupled to thegrip control shaft 574 by an arm linkage 590. The arm linkage 590 hasone end connected to the grip control shaft 574 by a pin 592 and anopposite end connected to the arm 582 by a ball 594 and socket 596connection, as shown in FIGS. 38 and 39.

With references to FIGS. 38 and 39, shifting the grip control shaft 574in direction 598 toward the inserter tool proximal end portion 504pivots the plate engagement arm 582 about a pin 600 of the pivot body524 and brings a tip 602 of the plate engagement are 582 toward a tip604 of the fixed arm 584. Due to the threaded engagement between theknob 572 and the grip control shaft 574, turning the knob 572 in aclockwise direction (as viewed from behind the tool 500) would producethe movement of the grip control shaft 574 in direction 598. Conversely,turning the knob 572 counterclockwise and moving the grip control shaft574 in direction 606 toward the inserter tool distal end portion 502pivots the plate engagement arm 582 in an opposite direction about thepin 600 and moves the tip 602 of the plate engagement arm 582 away fromthe tip 604 of the plate engagement arm 584. By moving the tip 602 ofthe plate engagement arm 582 away from the tip 604, the arms 582, 584can exert a compressive force against a wall 610 of the bone plate slot586 and engage the inserter tool distal end portion 502 to the boneplate 12, shown in FIGS. 40 and 41.

With reference to FIGS. 42 and 43, the handle 506 may have a recessedarea 620 sized to provide clearance for the lever 508 and a lever pivotpin 622 for connecting the lever 508 to the handle 506. With the lever508 connected to the lever pivot pin 622, a transmission end 624 of thelever 508 may be connected to a lever bolt 626 mounted on theintermediate pivot shaft 620, as shown in FIGS. 29 and 34. Thetransmission end 624 of the lever 508 has a slightly elongated opening630 that is sized to permit the lever bolt 626 to travel along theopening 630. The slight elongation of the opening 630 may be desirableto accommodate the linear movement of the lever bolt 626 and therotational, pivoting movement of the transmission end 624 of the lever508.

The components of the inserter tool 500 may be made of various materialsthat preferably can be sterilized to permit cleaning of the insertertool 500. In one form, the components are made of various metals andalloys, such as stainless steel.

With reference to FIGS. 44-52, a method of installing the bone platesystem 12 including using the inserter tool 500 is shown. Initially, thedistal end portion 502 of the inserter tool 500 is connected to the boneplate 12 and the implant pivot lever 508 of the inserter tool 500 ismoved to the open position away from the handle 506 to orient the boneplate 12 in the insertion orientation, as shown in FIG. 44. The insertertool 500 and connected bone plate 12 are positioned in a generallyvertical orientation above a working channel 700 formed by a retractor702. The inserter tool 500 is then moved downward in direction 710 toadvance the distal end portion 502 and the bone plate 12 connectedthereto into the working channel 700 until an end 712 of the bone plate12 is adjacent a surgical site 714. In the illustrated approach, thesurgical site 714 is adjacent a pair of vertebrae 720, 722 and animplant 724 therebetween (see FIG. 46).

Once the end 712 o the bone plate 12 has reached the surgical site 714,the implant lever 508 is moved toward the handle 506 to pivot the boneplate 12 and move the bone plate 12 from a generally parallelorientation relative to the vertebrae 720, 722 into a generallyperpendicular orientation, as shown in FIGS. 45 and 46. Further, theretractor 702 has blades with distal ends 715 that can be angled toextend generally obliquely relative to the working channel 700. Thisretracts the tissues adjacent the surgical site and provides room forpivoting of the bone plate 12 while maintaining a generally narrowworking channel 700.

A centering sleeve 800 is then advanced through the working channel 700and connected to the static throughbore 22 before a temporary fixationpin 802 is advanced down a cannula of the centering sleeve 800 and usedto temporarily fix the bone plate 12 to the vertebrae 720. The insertertool 500 may then be disconnected from the bone plate 12 and removedfrom the working channel 700. A second centering sleeve 810 issubsequently advanced through the working channel 700 to connect adistal end portion 811 of the centering sleeve 810 to the support member16, as shown in FIG. 47. The centering sleeve 810 has a proximal portion813 that may be manipulated by the surgeon to cause movement of thedistal end portion 811 and support member 16 connected thereto. Morespecifically, the distal end portion 811 of the second centering sleeve810 may be moved in direction 812A or 812B to move the support member 16in direction 48A or 48B along axis 47 of the elongate throughbore 18(see FIG. 11). The centering sleeve 810 preferably has a length thatpositions the proximal end portion 813 outside of the working channel700 while the distal end portion 811 is connected to the support member16 to improve the ease of manipulation of the position of the supportmember 16. Thus, the second centering sleeve 810 may be used to adjustthe position of the support member 16 along the elongated throughbore 18from outside of the working channel 700 and adapt the bone plate 12 tothe anatomy of the patient.

For example, if the implant 724 has a relatively large thickness 804,the opening 53 of the support member 16 may not be aligned with of thevertebrae 722 when the bone plate 12 is initially pivoted to thepositioning orientation shown in FIG. 46. The centering sleeve 810 canthen be moved in direction 812A to move the support member 16 indirection 48A and position the support member opening 53 above thevertebrae 722.

Once the support member 16 is positioned at a desired location along theelongated throughbore 18, the second centering sleeve 810 may be removedfrom the working channel 700 and the drive tool 2000 connected to thebone anchor assembly 20. Connecting the driving tool 2000 to the boneanchor assembly 20 includes advancing a drive tip 2002 of the drivingtool 2000 through the opening 400 of the cap drive member 34 and intoengagement with the drive recess 280 (see FIGS. 18 and 26). Connectingthe driving tool 2000 to the bone anchor assembly 20 may also includeconnecting the retention shaft 2004 of the tool 2000 with retentionthreads 284 of the bone screw 46, as shown in FIG. 48. The driving tool2000, with the bone anchor assembly 20 connected thereto, can then beadvanced through the working channel 700 and to advance a shank 725 ofthe bone screw 26 into the support member opening 53. (It is noted thatvertebrae 720, 722 and implant 724 are removed from FIGS. 48-52 forclarity purposes.) The driving tool 2000 is then used to drive the boneanchor 26 into the underlying vertebrae 722, as shown in FIG. 49.

Next, the drive tool 2000 is used to drive the bone anchor assembly 24into the fixed throughbore 22 using a similar approach taken withrespect to bone anchor 20, as shown in FIGS. 49 and 50. With the bonescrews 26 of the bone anchor assemblies 20, 24 holding the bone plate 12against the vertebrae 720, 722, a final tightener 3002 is advanced intothe opening 400 of the cap drive member 34 of the bone anchor assembly24 (see FIG. 26) and turned in direction 737 to shift the cap drivemember 34 to the locked position. Turning of the final tightener 3002and the resulting movement of the cap drive member 34 toward its lockedposition causes the cap drive member 34 to expand the locking cap 36.This tightly engages the locking cap 36 with the seating surface 120 ofthe throughbore 22.

The locking tool 3000 is then advanced into the opening 400 of the capdrive member 34 of the bone anchor assembly 20 and turned to move thecap drive member 34 toward the locked position. This expands the lockingcap 36 of the bone anchor assembly 20 and tightly engages the lockingcap 36 with the seating surface 103 of the support member 16. Thisshifts the portions 70, 72 of the support member 16 apart in directions76, 78 against the throughbore walls 80, 82 (see FIG. 7) and therebyfixes the position of the support member 16 along the elongatedthroughbore 18. Further, because the cap drive member 34 is threadinglyengaged with the bone screw head 30, shifting the cap drive member 34 tothe locked position tightly engages the cap drive member 34 to the head30 as well as the locking cap 36 therebetween. In this manner, the boneanchor assembly 20 is firmly engaged with the support member 16 which isin turn firmly engaged to the plate member 14 at the desired locationalong the throughbore 18.

With respect to FIGS. 53-61, an inserter tool 1000 is provided forpositioning the bone plate 12 near one or more bones. The inserter tool1000 is substantially similar to the inserter tool 500 described abovesuch that the differences between the inserter tools 500, 1000 will behighlighted. One difference between the inserter tools 500, 1000 is thatthe inserter tool 1000 has components that can be partially disassembledand pivoted generally about an axis 1002 at a distal end 1004 of theinserter tool 1000, as shown in FIG. 54. The ability to partiallydisassemble and pivot the components of the inserter tool 1000 allowsthe inserter tool 1000 to be cleaned without complete disassembly of thetool 1000.

More specifically, the inserter tool 1000 has an outer body shaft 1010and a partial pivot sleeve 1012 for controlling pivoting of a pivot body1014. The distal end of the pivot sleeve 1012 is connected to the pivotbody 1014 at a pin 1030 so that translational movement of the pivotsleeve 1012 produces pivoting of the pivot body 1014. The inserter tool1000 has a lever 1016 connected to the pivot sleeve 1012 for controllingpivoting of a pivot body 1014 at the distal end 1004 of the insertertool 1000. Moving the pivot lever 1016 toward a handle 1018 of theinserter tool 1000 shifts the pivot sleeve 1012 in direction 1020 towarda proximal end 1019 of the inserter tool 1000 and pivots the pivot body1014 about a pin 1022. A spring 1019 may bias the handle 1018 toward anopen position to limit unintentional pivoting of the pivot body 1014 andbone plate 12 connected thereto.

The lever 1016 is connected to the handle 1018 by a pin 1060 receivedwithin a slot 1062 of the handle 1018 (see FIGS. 55, 57). The lever 1016has a transmission end 1070 with a recess 1072 sized to receive a tab1074 of the pivot sleeve 1012, as shown in FIG. 56. The tab 1074 of thepivot sleeve 1012 rides in the recess 1072 during back and forthmovement of the pivot sleeve 1012. During disassembly of the insertertool 1000, the lever 1016 can be shifted in direction 1064 (see FIG. 53)to disengage the transmission end 1070 of the lever 1016 from the tab1074 of the pivot sleeve 1012. With the lever transmission end 1070disengaged from the pivot sleeve 1012, a proximal end 1073 of the pivotsleeve 1012 can be pivoted in direction 1075 away from the pivot body1014, as shown in FIG. 54. Pivoting the pivot sleeve 1012 in direction1075 moves the pivot sleeve 1012 about the pin 1030 which connects thepivot sleeve 1012 to the pivot body 1014.

Another difference between the inserter tools 500, 1000 is that theinserter tool 1000 has a grip control shaft 1050 and a grip adjustmentmember 1090 engaged with threads 1092 of the grip control shaft 1050.The grip adjustment member 1090 is captured by the threads 1092 betweenan enlarged knob 1094 of the grip control shaft 1050 and a collar 1096of the body shaft 1010. The grip adjustment member 1090 is turnedclockwise or counterclockwise to produce proximal or distal longitudinalmovement of the grip control shaft 1050 by way of the engagement betweeninternal threads of the grip adjustment member 1090 and the threads 1092on the grip control shaft 1050.

During disassembly, the knob 1094 is turned ninety degrees clockwise torotate a foot 1095 of the grip control shaft 1050 into a recess 1097 ofthe pivot body 1014 (see FIGS. 55 and 57). The grip adjustment member1090 is then turned to produce longitudinal movement of the grip controlshaft 1050 toward the proximal end of the inserter tool 1000 until thethreads 1092 of the grip control shaft 1050 disengage the internalthreads of the grip adjustment member 1090. Next, the knob 1094 isgrasped and pulled in direction 1099 (see FIG. 54) to withdraw the gripcontrol shaft 1050 from within the outer body shaft 1010. At this point,the pivot sleeve 1012 is pivoted away from the outer body shaft 1010 andthe grip control shaft 1050 has been withdrawn from the outer body shaft101. Because both the pivot sleeve 1012 and grip control shaft 1050 areseparated from the body shaft 1010, the surfaces of the body shaft 1010,pivot sleeve 1012, and grip control shaft 1050 may be easily accessedand cleaned. Further, as shown in FIG. 55, the body shaft 1010 has agenerally C-shaped cross section with an opening 1100 along one sidethereof and the pivot shaft 1012 has a generally U-shaped cross sectionwith an opening 1102 along one side thereof. The cross sections of thebody shaft 1010 and the pivot shaft 1012 provide ready access to theinternal surfaces of the body shaft 1010 and the pivot shaft 1012 sothat the internal surfaces may be easily cleaned.

While there have been illustrated and described particular embodimentsof the present invention, it will be appreciated that numerous changesand modifications will occur to those skilled in the art, and it isintended in the appended claims to cover all those changes andmodifications which fall within the true spirit and scope of the presentinvention.

What is claimed is:
 1. A bone anchor assembly for securing a bone plateto a bone, the bone anchor assembly comprising: an elongate bone anchorhaving a longitudinal axis; a head of the bone anchor and a shankdepending therefrom, the shank extending along the longitudinal axis; aresilient locking cap associated with the head of the bone anchor, theresilient locking cap extending about a portion of the bone anchor head;a cap drive member having a depending annular wall for fitting about thebone anchor head portion and being disposed radially between the boneanchor head portion and the locking cap, the cap drive member beingshiftable axially along an outer periphery of the bone anchor headportion from an unlocked to a locked position; and engagement surfacesof the annular wall and the locking cap that are configured to engageand radially expand the locking cap with the engagement surfaces engagedabout and radially adjacent to the bone anchor head portion as the capdrive member is shifted axially from the unlocked to the lockedposition.
 2. The bone anchor assembly of claim 1 wherein the dependingannular wall of the cap drive member has a radially inner portion havingconnecting structure for being connected to the bone anchor head portionand a radially outer portion with the annular wall engagement surfacedisposed thereon.
 3. The bone anchor assembly of claim 1 wherein theengagement surfaces of the annular wall and locking cap are cam surfacesthat extend obliquely to the longitudinal axis of the bone anchor. 4.The bone anchor assembly of claim 1 wherein the cap drive member has anupper drive portion configured to be engaged by a drive tool forshifting the cap drive member from the unlocked to the locked position,and the depending annular wall extends axially away from the cap drivemember upper drive portion.
 5. The bone anchor assembly of claim 1wherein the bone anchor head includes an upper drive recess forreceiving a drive tool for driving the bone anchor into bone and the capdrive member has an axial through opening axially aligned with the upperdrive recess for allowing the drive tool to be advanced through theaxial through opening and into the upper drive recess.
 6. The boneanchor assembly of claim 1 wherein the depending wall of the cap drivemember is disposed between the engagement surface of the locking cap andthe bone anchor head portion as the cap member is shifted between theunlocked and locked positions.
 7. The bone anchor assembly of claim 1wherein the bone anchor head comprises a shoulder bearing surface and anannular wall upstanding therefrom that includes the bone anchor headportion, the bearing surface being configured to support the locking capfor sliding thereon as the locking cap is radially expanded.
 8. The boneanchor assembly of claim 1 wherein the bone anchor head comprises apartially spherical outer surface portion having a predetermined radiusof curvature and the locking cap has a partially spherical outer surfacehaving substantially the same radius of curvature as the bone anchorhead partially spherical outer surface portion so that with the capdrive member shifted to the locked position and the locking cap radiallyexpanded, the outer surface portion of the bone anchor head and theouter surface of the cap drive member are substantially flush to combineto form a larger partially spherical surface.
 9. A bone plate systemincluding the bone anchor assembly of claim 8, the bone plate systemcomprising: a bone plate having an opening sized to receive the boneanchor head and locking cap and cap drive member associated therewith;and an annular surface extending about the bone plate opening configuredto engage both the bone anchor head outer surface portion and thelocking cap outer surface when the bone anchor is driven into the boneplate opening and the locking member is shifted to the locked position.10. The bone anchor assembly of claim 1 wherein the bone anchor head andthe locking cap have substantially flat confronting surfaces configuredto restrict axial movement of the locking cap along the bone anchorhead, and the cap drive member and the locking cap have substantiallyflat confronting surfaces configured to restrict axial movement of thecap drive member relative to the locking cap such that the substantiallyflat confronting surfaces of the bone anchor head, locking cap, and capdrive member maintain the bone anchor member, locking cap, and cap drivemember in a preassembled configuration with the cap drive member in theunlocked position.
 11. The bone anchor assembly of claim 1 wherein thebone anchor head and the cap drive member are rigid.
 12. The bone anchorassembly of claim 1 wherein the locking cap has a split-ringconfiguration.
 13. A bone plate system for stabilizing a plurality ofbones, the bone plate system comprising: a bone plate; a plurality ofthroughbores of the bone plate; a plurality of bone anchors forinserting into the throughbores each having a head at one end thereof;an actuator device carried on one of the bone anchor heads for beingdriven between unlocked and locked positions; at least one of thethroughbores being elongated along the boneplate and having oppositeends and a longitudinal axis extending therebetween; a resilient supportmember received in the elongated throughbore and axially movabletherealong, the support member having an opening therein sized toreceive the one bone anchor head and actuator device carried thereon andbeing configured to expand as the actuator device is driven between theunlocked and locked positions; and interfering portions of the supportmember and the bone plate that are configured to be shifted to a lockedorientation relative to each other with driving of the actuator deviceto the locked position to keep the support member and the one boneanchor head therein locked at a preselected axial position in theelongated throughbore against axial movement toward either end thereof.14. The bone plate system of claim 13 wherein the one bone anchor headand the actuator device carried thereon are threaded to each other sothat with the actuator device driven to the locked position, theactuator device is substantially rigidly screwed to the one bone anchorhead.
 15. The bone plate system of claim 13 wherein the support memberhas a body portion with a predetermined width transverse to thelongitudinal axis of the elongated throughbore that is sized to maintainthe interfering portions of the support member and the bone plate in anadjustment orientation and permit movement of the support member towardeither end of the elongated throughbore until the one bone anchor headand actuator device carried thereon have been received in the supportmember opening and the actuator device has been driven to the lockedposition.
 16. The bone plate system of claim 13 wherein the actuatordevice comprises a locking member connected to the head of the one boneanchor and a resilient cap associated with the bone anchor head, thelocking member being configured to shift along the bone anchor head andradially expand the resilient cap as the actuator device is drivenbetween the unlocked and locked positions.
 17. The bone plate system ofclaim 13 wherein the support member has a partially spherical innersurface extending about the opening thereof and the actuator device hasa partially spherical outer surface that is configured to tightly engageand mate with the partially spherical inner surface of the supportmember with driving of the actuator device to the locked position. 18.The bone plate system of claim 17 wherein the head of the one boneanchor has a partially spherical outer surface configured to engage thepartially spherical inner surface of the support member so that both thebone anchor partially spherical outer surface and the actuator devicepartially spherical outer surface engage the support member partiallyspherical inner surface with the bone anchor head and actuator devicecarried thereon received in the support member opening and the actuatordevice has been driven to the locked position.
 19. The bone plate systemof claim 13 wherein the elongated throughbore includes a pair ofsubstantially straight axially extending guide surfaces and the supportmember includes substantially straight axially extending sidesconfigured to abut the guide surfaces of the throughbore and restrictrotary movement of the support member in the throughbore.
 20. The boneplate system of claim 19 wherein the elongated throughbore has a narrowsection and the support member has a narrow portion sized and configuredto fit within the narrow section of the throughbore, the narrow sectionof the throughbore including the substantially straight axiallyextending guide surfaces and the narrow portion of the support memberincluding the substantially straight axially extending sides configuredto abut the guide surfaces.
 21. The bone plate system of claim 13wherein the actuator device has an outer surface; and the support memberhas a wall portion extending about the opening of the support member andaxially along the majority of the outer surface of the actuator devicesubstantially the entire length thereof for maximizing surface contacttherebetween.
 22. The bone plate system of claim 13 wherein theinterfering portions of the support member and the bone plate comprisesets of interfering portions disposed on opposite sides of the supportmember and the one throughbore.
 23. A method of securing a bone plate toa bone, the method comprising: moving a resilient support memberdisposed within an elongated throughbore of the bone plate along alongitudinal axis of the throughbore to a selected axial position alongthe throughbore; advancing a shank of a bone anchor into a throughopening of the support member and into the bone; seating a head of thebone anchor and an actuator device carried thereon in the throughopening of the support member; driving the actuator device from anunlocked to a locked position; expanding the support member toward wallsof the elongated throughbore as the actuator device is driven to thelocked position; and locking the support member and the bone anchor atthe selected axial position along the throughbore.
 24. The method ofclaim 23 wherein driving the actuator device from the unlocked to thelocked position comprises shifting a locking member of the actuatordevice along the head of the bone anchor from an unlocked position to alocked position and radially expanding a resilient cap of the actuatordevice.
 25. The method of claim 23 wherein locking the support memberand the bone anchor at the selected axial position along the throughborecomprises moving interference portions of the support member and thebone plate into a locked orientation which restricts axial movement ofthe support member along the throughbore.
 26. The method of claim 23wherein locking the support member and the bone anchor at the selectedaxial position along the throughbore comprises fixing the actuatordevice to the bone anchor head and tightly engaging the actuator devicewith the support member.
 27. The method of claim 23 wherein moving thesupport member along the longitudinal axis of the throughbore comprisesmoving the support member while interference portions of the supportmember and the bone plate are in an adjustment orientation.
 28. Themethod of claim 23 wherein seating the head of the bone anchor and theactuator device carried thereon in the through opening of the supportmember includes seating a partially spherical outer surface of the boneanchor head against a partially spherical seating surface of the throughopening of the support member.